net/smc: simplify test_link function usage

Make smc_llc_send_test_link() static and remove it from the header file.
And to send a test_link response set the response flag and send the
message back as-is, without using smc_llc_send_test_link(). And because
smc_llc_send_test_link() must no longer send responses, remove the
response flag handling from the function.

Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>